Copolymerization of PEO Macromonomers with Styrene

The rate of dispersion copolymerization of PEO-MA macromonomer and styrene was found to increase with increasing initiator concentration VA - water soluble, DBP (dibenzoyl peroxide) - oil soluble, [PEO-MA] =0.06 mol dnr3, [styrene] =2.13 mol dm-3, in ethanol/water, v/v4/l) [65,66]  

Exponents 0.6 and 0.8 deviate from both the homogeneous nucleation and micellar models. Thus the bimolecular termination between the growing radicals is suppressed. This behavior may also result from the surface activity of the graft copolymer formed. The higher the surface activity of graft copolymer the higher the particle number. This behavior would indicates that the graft copolymer formed within the particles (with DBP) is more efficient. 

One of the common approaches to infer the termination mechanism is based on the evaluation of the dependence of the molecular weight on the initiator concentration. The following dependences [67] 

The molecular weights increase with conversion and the increase is much more pronounced for the VA runs. The strong increase of molecular weight with conversion results from the transfer of reaction loci from the solution to the polymer particles. At low conversion the polymers are mostly formed in the continuous phase in which the termination rate is high. In polymer particles the local concentration of monomer is much higher than that in the continuous phase and, therefore, the growth events are favored in the polymer particles. 

The molecular weights of polymer products of the DBP runs are relatively low and very similar to those in the solution copolymerization [69]. These results in- 

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